Knorpels

Knorpels, or cartilage, are avascular connective tissues found throughout the vertebrate body. They consist of chondrocytes embedded in an extracellular matrix rich in collagen (primarily type II in hyaline cartilage) and proteoglycans, with high water content. This composition gives cartilage both resistance to compression and elasticity while remaining pliable.

There are three main types of cartilage. Hyaline cartilage provides smooth surfaces for joint movement and supports soft tissues. Fibrocartilage is tougher and more resistant to shear, found in intervertebral discs, menisci, and the pubic symphysis. Elastic cartilage contains elastic fibers, which confer resilience, and is found in the ear, epiglottis, and the auditory tube.

Cartilage occurs at articular surfaces of joints, in the rib cage, in the nose and ears, in the trachea and larynx, and in the growth plates of developing bones. Its primary roles are to cushion joints, distribute loads, maintain airway structures, and shape and support facial features. In children, cartilage also guides bone growth, which later ossifies through endochondral development.

Growth and repair of cartilage are limited by its avascularity. Nutrients reach chondrocytes by diffusion, leading to slow healing after injury. Growth occurs via appositional growth from the perichondrium and interstitial growth within the cartilage matrix; articular cartilage, which typically lacks a perichondrium, has especially restricted repair capacity.

Clinically, degeneration or injury of articular cartilage is central to conditions such as osteoarthritis. Treatments include surgical techniques to stimulate repair, such as microfracture, autologous chondrocyte implantation, or grafts, as well as ongoing research into regenerative therapies.